Regarding rotating carry ammo, I work behind a desk and carry concealed, with the ammo well protected from moisture. If the ammo has come in contact with moisture (usually from sweat but very occasionally from rain), it gets replaced. I always chamber the same round, and replace it if it starts getting shorter.
Within the past decade I have seen two ammo shortages lasting multiple years, when nothing was available. I have since begun keeping more here, but this is one reason I have disliked getting rid of what is likely perfectly good, expensive ammo rather than shooting less expensive ammo.
1 in every 15 rounds failing to go off on the first primer hit is concerning. The ammo was carried for much longer than most here would consider wise and I will have to re-think what I do. However, nothing happened to that ammo in that time. The problem was at least as likely to be poor quality ammo than ammo that was carried too long.